Cross-linked olefin-maleic anhydride interpolymers and salts thereof



United States atet Patented Jan. 12, i9

3,165,486 CROSS-LINKED OLEFIN-MALEIC ANHYDRIDE INTERPOLYMERS AND SALTS THEREOF John H. Johnson, Dayton, Ohio, assignor to Monsanto Company, a corporation of Delaware No Drawing. Filed Sept. 29, 1958, Ser. No. 763,796 26 Claims. (CL 26029.7)

This invention relates to crosslinked C -C olefin and maleic anhydride interpolymers and salts thereof, and particularly to interpolymers of ethylene, propylene, n-butylene, and/ or isobutylene with maleic anhydride using as vinyl ester of an olefinically unsaturated carboxylic acid as the cross-linking agent, and to aqueous disper-,

sions of alkali, amine or ammonium salts thereof. This application is a continuation-in-part of my copending applications Serial Nos. 712,680 and 712,681; both now abandoned, filed February 3, 1958.

Many cross-linking agents are known for use in the production of cross-linked styrene-maleic anhydride polymers and others. US. 2,647,886 teaches a large nimber of cross-linking agents suitable for use with styrene and maleic anhydride comonorners. It appears from the teachings of this patent that any one of the cross-linking agents named therein as well as many not named would be suitable for cross-linking styrene and maleic anhydride in polymers.

Surprisingly, I have found that a number of tritiumtional compounds which might be expected to be good cross-linking agents for C -C olefins and maleic anhydride comonorners are not at all suitable especially for my particular purpose namely for preparing interpolymers useful as thickeners for textile printing pastes. For example, the following bifunctional compounds were tested using 1% by weight cross-linking agent based on reacting monomers and standardized polymerization conditions with ethylene and maleic anhydride comonomers: divinyl benzene, N,Ndialkyl toluenesulfonamide, vinyl allyl ether, triallyl isocyanurate, diallyl cyanamide, triallyl cyanurate, and ethylene glycol dimethacrylate. None of these compounds proved to be effective or usable. It is most surprising that divinyl benzene which proved to be an excellent cross-linking agent for styrene and maleic anhydride comonorners as indicated in US. 2,647,886, gave no appreciable cross-linking with ethylene and maleic anhydride resulting in a dimethylforrnamide soluble polymer even when the amount of divinyl benzene was increased above 2% based on reacting monomers. Ethvlene glycol dimethacrylate taught in this patent as a crosslinking agent does not cross-link my product either.

Also. the following bifunctional compounds tested with propylene and maleic anhydride were found to be ineffective: divinyl carbitol, divinyl sulfone, vinyl 'allyl ether, N,N-met-hylenebisacrylamide, and divinyl benzene. Again, divinyl benzene which proved to be an excellent cross-linking agent for styrene and maleic anhydride, gave no appreciable cross-linking with propylene, and maleic anhydride. In other words, divinylberzene and these other cross-linking agents which are ndicated to be ineffective just do not cross-link either eth lene or propylene and maleic anhydride copolymers to any measurable extent. The results, of course, would be expected to be the same wherein the olefin comono; was isobutylene or n-butylene.

It is a primary object of this invention to provide cr linked C -C olefin and maleic anhydride interpolyn usable in salt form as thickeners in textile printing p2 These and other objects of the invention will becl apparent as a detailed description of the invention 1 ceeds.

Broadly, the invention comprises reacting C -C ole with 1,2-dichrboxylic acids and their derivatives in presence of the vinyl ester cross-linking agents. dicarboxylic acids can be maleic acid, furnaric acid, mono or dichloro substituted maleic and furnaric at alkylated maleic and fumaric acids, mono and diph| maleic acids, benzyl maleic acid, dibenzyl maleic a ethyl maleic acid or any similar acids containing a do:

- bond in the chain between the carboxyl groups sucl mesaconic and citraconic acids. Acids where the dor bond has shifted from the 1,2 position, such as itacl and glutaconic acid can also be used. However, the hydride of each of the above acids capable of anhyd formation will normally be preferred rather than acids.

More narrowly, the interpolymers of the invention formed by polymerizing a monomeric mixture of ma anhydride and a C -C olefin or olefin mixture usin cross-linking agent which is a vinyl ester of an olefinic unsaturated carboxylic acid having from 3 to 24 car atoms in an amount in the range of about 0.1 mol pen and about 5 mol percent, preferably from about 0.3 percent to about 3 mol percent, based on reacting mc mers. Normally with ethylene, it will be preferred the interpolymer be produced using about 4:1 or big molar ratio of ethylene to maleic anhydride even tho they react to form the interpolymer in substantially a molar ratio; however, the interpolymer can be m using a larger or smaller molar ratio. If the olefir charged in a molar excess as compared to the maleic hydride the amount of the reacting monomers are ea calculated from the amount of maleic anyhdride char to the reaction vessel and the assumption that an ec molar amount of olefin reacts therewith. This assu: tion has proven to be true to a sufiiciently close deg that no practical error results from its assumption.

'As has been indicated the interpolymers of the int tion are formed from maleic anhydride and a C -C fin, i.e. ethylene, propylene, n-butylene, and lSOblllYlt using as a cross-linking agent a vinyl ester of an olet cally unsaturated carboxylic acid having from 3 to carbon atoms. An illustrative but non-limiting list cross-linking agents is as follows: The vinyl esters acrylic acid, methacrylic acid, crotonic acid, isocrotc acid, vinylacet'icacid,'Z-pentenoic acid, 3-rnethyl-2hexc ic acid, Z-hexenoic acid, Z-heptenoic acid, methyl-2- tenoic acid, 2-nonenoic acid, -9-decylenic acid, stillir acid, 9-dodecylenic acid, palmitoleic acid, oleic acid, rii oleic acid. petroselenic acid, vaccenic acid, linoleic a linolenic acid, eleostearic acid, licanic acid, parinarica gadoleic acid, arachidonic acid, cetoleic acid, erucic at nervonic acid, etc. Gther suitable vinyl esters are the vi or divinyl esters of unsaturated dicarboxylic acids such the following: vinyl maleate, divinyl maleate, vinyl fur tte, divinyl fumarate, vinyl itaconate, divinyl itacouate, nyl citraconate, divinyl critraconate, vinyl mesaconate, .vinylmesaconate, vinyl glutaconate, divinyl glutaconate,

For use as thickeners in textile printing pastes the inrpolymers should be made using at least an amount of .e cross-linking agent suflicient to make 'interpolymers hich are substantially insoluble, i.e. at 2% polymer con- :ntration do not form a clear solution but rather a ixotropic gel, in dimethylformamide at 25 C., and they e used as thickeners in the form of an alkali metal (i.e. dium, potassium, lithium, rubidium or cesium), amine id/or ammonium salts forming a dilute swollen gel or spersion in aqueous medium. When polymeric anhy- "ides are dissolved using ammonia or amine bases, an preciable amount of amide groups are formed resulting mixed ammonium-amide or amine-amide polymeric vlts, but if the anhydridcs are first hydrolyzed to the acid :forc neutralization the salts will be preponderantly amg onium or amine salts. The term amine salt will b :ed generically throughout this specification and the aims thereof to cover the ammonium salts, the amine vlts, the ammonium-amide salts, and the amine-amide lts; however, in some cases the term ammonium sal'; ill be used generically to cover only ammonium and nmonium-arnide salts. Mixtures of alkali metal and nine salts can, of course, also be used, if desired and .ese mixed salts would be substantially equivalentto ther alone. The amines which are preferred are the wer alkyl primary and secondary amines such as methyl nine, dimethyl amine, ethyl amine, diethyl amine, the ropyl amines, the dipropyl amines, n-hexyl amine etc. iowever, longer chain amines such as stearyl or palmityl ."imary or secondary amines, etc., or even polyamines ich asethylenediamine or diethylenetriamine, etc., can desirable for special uses. For comparison of properes an arbitrarily selected l /z% by weight aqueous disferent types of thickeners. The emulsion can be formed by mixing an aqueous dispersion of my salt with a petroleum solvent. However, it should be understood that my salts can be used as a print paste vehicle resin in a completcly aqueous system without the petroleum solvent, particularly the higher cross-linked and/ or higher molecular weight material. After application of the dye to the fabric the fabric is dried and sometimes aged for color fastness. Aging and drying can be accomplished by steaming the fabric.

The novel cross-linked interpolymers or salts thereof are also useful as thickeners in fluids used in depleted oil wells to increase oil recovery by displacing oil from the oil sands. This process is referred to in the trade as water-base fracturing. Normally these water-base fracturing" fluids are used to carry sand into the formation to aid in the oil displacement. For this use the thickeners are especially effective in the form of hydrolyzed interpolymers or in the ammoniatcd form which would provide amide-ammonium salts of the interpolymers. To these water-base fracturing fluids containing the novel thickeners of the invention can be added fluid-loss or other additives, if desired. Acids such as HCl are normally used to break gels in the two-step process wherein the acid is added after the gel is pumped into the formation. Rather than adding the agent to break the gel after pump ing the gel into the formation, the gel-breaking agent can :rsion of the interpolymer salt having a pH in the range f about 7 to about 11 for alkali metal salts, preferably 0m 8 to about 10, is chosen, since these pH values repreant the upper range of the viscosities associated with the a'proach to full neutralization of all carboxyls, but aque- .ls viscosities are still quite high and useful even with to pH as low as 5. In the case of amine salt viscositie.v 'e high in the range of about 4 to about 10 pH, but the referred range is about 5 to about 7 pH. These 1 /2% eight dispersions in water of the salts for greatest ef- :iency as printing paste thickeners have a viscosity greater tan 10,000 centipoises at 25 C., preferably greater than ),000, andthe viscosity can be greater than 100,000 :ntipoises at 25 C. Less of a higher molecular weight. higher cross-linked interpolymer salt is required fo le printing paste, than if a lower molecular Weight or wer cross-linked material is used. The salt can be used aqueous dispersion in water in an amount of about :tween about 0.1% and about 15% by weight, prefer- Jly. 0.25 to about 10%, in formulating the textile printig pastes. The pH range should be chosen to yield .aximum useful viscosities in accordance with the partic- .ar base used and with consideration of the pH require- .ents and limitations of. the particular system to be ickened.

Some types of coloring materials such as pigments or les used for printing cotton, rayon, nylon and other fabcs are already handled as high concentrations of the pigent (dye) dispersed in an inorganic solution of synthetic sin. They are applied by conventional means such as I rollers to the fabric in the form of a pigment-in-water nulsion. The emulsion is prepared by dispersing a :troleum solvent in an unpigmented resin solution called clear, e,g., see Example 4 of US. 2,364,692. My vel thickener in the salt form could, for example, be .bstituted for the ethyl cellulose of Example 4 of the rtent with proper adjustment as to amount to compensate Ir differences in efiiciency of thickening of these two difbe incorporated in the fluid before it is pumped into the formation. In this latter case, however, the gel breaker must be slow acting and not break the gel until the fluid has been pumped into the formation. For example, sodium acid tetrametaphosphate can be suitable gel-breaker for addition to fracturing fluids using my novel thickeners since it will degrade slowly by scission to produce a very acid solution. Also the salts of the half-amide half-acid form of the cross-linked in-terpolymers can be used as the thickener for oil drilling muds.

The novel interpolymers, the hydrolyzed products, and salts thereof, can be additionally used in the formation of various mucilaginous or colloidal gel applications such as dentifrices, talc suspensions used in making dental impres-- sions, bread dough, surgical jellies, creams and ointments,

bulk laxatives, generally as thickencrs for aqueous sys-- terns (cg. latex paints), carrying agents, ion-exchange resins and other materials for use in treatment of various disorders of the human and animal gastro-intestinal tract, etc. Also, they can be used as suspending agents for flocculation treatment of ores for concentration or beneficiation or mineral dressing, especially iron, uranium, rare earth metals and molybdenum ores, etc. A further use is in industrial or sewage waste waters for coagulation to clean up the water before dumping in a stream, e.g. paper mill waste water. Yet another use is to help suspend fines and improve uniformity of fibers in paper manufacture. For some of these uses the pH of the salt would be varied from substantially below 3 to substantially above 11 depending on the particular properties that may be desired.

In making the new interpolymer, conditions conventionally used in the preparation of olefin-maleic anhydride copolymers are suitable and peroxide catalysts are used in the polymerization. Preferred conditions fall within the range of about 0 to C. preferably about 30' to about 100 C., and about 0 to about 600 p.s.i.g. depending on the particular olefin used. Radiation polymerization can also be used to produce the novel interpolymers elg. using such high-energy radiation sources as X-rays,

out the cross-linking as a separate chemical reaction or An aromatic hydrocarbon solvent polymerization step. It is rather preferred to add the cross-linking agents to the maleic anhydride and olefin comonomer during the initial polymerization step since more stable and more improved interpolymers result.

The invention will be more clearly understood from the following detailed description of specific examples thereof:

EXAMPLE 1 A three liter rocking autoclave was charged with 267 grams of maleic anhydride, 2089 cc. of ethylene dichloride, and 3.71 grams of benzoyl peroxide polymerization catalyst. The autoclave (bomb) was pressurized to 100 pounds per square inch gauge (p.s.i.g.) with ethylene, rocked at room temperature for about minutes and the ethylene vented, This flushing operation was repeated once more to free the reaction mixture of dissolved air. The bomb was then charged with sutficient ethyldne to give an estimated 300 p.s.i.g. on heating to the reaction temperature of 70 C. Rocking of the bomb was started and the temperature brought up to 70 C. by means of an electrically heated jacket. Additional ethylene was charged into the bomb from time to time to maintain the bomb pressure at approximately 300 p.s.i.g. After about 16 hours at 70 C. during which time the absorption of ethylene had ceased, unreacted ethylene was vented. The total reaction mixture was filtered, and the separated ethylene-maleic copolymer washed with ethylene dichlo ride while filtering. The polymer was dried at 108 C. for about 12 hours under the full vacuum of a water aspirator, and the yield of 1:1 copolymer of ethylene and maleic anhydride was 342 grams.

The specific viscosity of this copolymer was determined at 25 C. by modification of ASTM method D 445-446T, method B, using an Ostwald viscosimeter. The copolymer was dissolved in 1 weight percent concentration in dimethylformamide and the specific viscosity determined. The specific viscosity was 0.532 at 25 C.

EXAMPLE 2 The experiment of Example 2 was run in a substantially identical manner to that of Example 1, except for changes in conditions and reactor charges indicated as follows:

Maleic anhydride grams 267 Ethylene p.s.i.g 450 Ethylene dichloride cc ,2089 Benzoyl peroxide grams 3.48 Vinyl crotonate do 11.71 Temperature C 60 The amount of vinyl crotonate represents 05% by weight or 0.28 mol percent based on reacting monomers, the

reaction time was about 17 /2 hours, and the yield of product polymer was 336 grams. I

A specific viscosity determination was attempted on the polymer produced in Example 2, but it was found that 1% of this polymer formed an insoluble gel in dimethylformamide, so no specific viscosity determination was possible.

A sample of. the polymer of Example 2 was added to sufficient water containing sodium hydroxide to make up a 1V2 concentration of the polymer in water, the sodium hydroxide having been added in sutficient amount to neutralize the maleic anhydride copolymer forming substantially the disodium salt of the polymer and giving a pH of 9.28. The resulting dispersion of the polymer salt in water was tested for viscosity with a Brookfield viscosimeter using a number 4 spindle at 6 rpm. Thegviscostly of the dispersion was 14,600 centipoises at room temperature (about 25 0).

EXAMPLE 3 The polymerization run of Example 3 was conducted in the same manner as was that in Example 2 except for changes in conditions and reactor charge indice follows:

Maleic anhydride grams Ethylene p.s.i.g Ethylene dichloride cc Benzoyl peroxide grams Vinyl crotonate do Temperature C The amount of vinyl crotonate represents 1.0% by 0.56 mol percent based on reacting monomers, the rt time was about 16 /2 hours, and the polymer yie 341 grams.

As in Example 2 an attempted specific viscos termination using 1% of the product polymer in dir formamide resulted in an insoluble gel, so no viscosity determination could be made.

In a similar manner to that described in Exan a 1/2% dispersion of the sodium salt of the poly Water was prepared having a pH of 10.0. A Bro viscosity determination of this aqueous dispersioi a viscosity of 31,000 centipoises at room temp (about 25 C.). This higher viscosity polymer, of resulted from an increased amount of cross-linking as compared to the polymer of Example 2.

EXAMPLE 4 A This experiment was the same as Example 3, that the polymerization conditionswere varied usi C. and 450 p.s.i.g. as indicated from the followin,

Maleic anhydride grams Ethylene p.s.i.g Ethylene dichloride cc Benzoyl peroxide grams Vinyl crotonate do Temperature C The reaction time was about 17 hours, and the y polymer was 346 grams. The polymer of this e: formed an insoluble gel in an attempted specific vi determination of 1% of the polymer in dimethyl mide.

In a similar manner to that described in Examp l/2% aqueous dispersion of the sodium salt of (hi mer was formed which had a pH of 10.15. A Bro viscosity determination of this aqueous dispersioi a viscosity of 68,400 cetipoises at room temperature higher viscosity material resulted from the higher It iar weight of the base polymer produced at the low:

. perature and higher pressure as compared to Exar EXAMPLE 5 In this experiment twice the amount of vinyl cro namely, 6.86 grams were charged to the autoclave a 2% by weight concentration, 1.12 mol percent, 0 crotonate in the final polymer. This experimei carried out in a similar manner to that of Example reactor conditions and reactor charge as follows:

Maleic anhydride grams Ethylene -p.s.i.g Ethylene dichloride .cc Benzoyl peroxide grams Vinyl crotonate do Temperature C The reaction time was about 15 hours, and the y polymer was 349 grams. The polymer of this e: formed an insoluble gel in an attempted specific vi determination of 1% of the polymer in dimethylfor In a similar manner to that described in Exam; l /2% aqueous dispersion of the sodium salt of tl ymer was formed with a solution pH of 10.8 Brookfield viscosity determination of this aqueoi persion gave a viscosity greater than 100,000 cent at 25 C., the exact viscosity not being determinabl was outside of the range of the particular instrument monomers) were charged with the other reactants to the ;cd. Viscosity determinations were made at lower conautoclave, which is indicated as follows:

:ntrations of 1% and 0.5% salt and these results were Maleic h d i 267 5,000 centipoises at pH 9.40 and 21,200 at pH 9.25, repropylene i 100 iectively- 5 Benzene cc 2089 Table I, which follows, summarizes the experiments Benzoyl peroxide "grams" 3.48 scussed in detail above and also a number of other ex- Vinyl acrylate do 3.43 :riments which were carried out. Temperature C..- 70 6 TABLE I ETHYLENE-MALEIC ANllYDRIDE Wt. Per- Bx. Cross Linking cent+(Mol 'lemp,, Press, S ec. pH Brookfleld to. Agent Percent) C. p.s.i.g. isc. Vise. ep.

X-Liuk 70 300 0.532 0.5(0.2s) 60 9.3 14,000 I 1.0(0.56) 70 10.0 31,000 1. 0(0. 56) 60 10.1 es, 400 2.0(1.12) 60 10.21 100,000

9.4 0e,000(1%) 9.2 I 21,200(0.5%) Vinyl acrylate 1.0(0.64) 70 300 9.4 9,000 do 2.00.28 00 450 9.5 100,000

9.3 100,000(1%) 9. e 23, 600 (0. do (1.2s) 70 300 10.1 100,000

PBOPYLENE-MALEIG ANHYDRIDE ISOBUTYLENE-MALEIC ANHYD RIDE Vinyl acrylato--- 1 The pressure in these runs was nutogenous.

A few general conclusions can be reached by examining 7 ese data, of Table I. Vinyl acrylate appears to be the iperior cross-linking agent usable with maleic anhydride 1d the C -C olefins generally. For ethylene and maleic ihydride only, vinyl crotonate is an excellent crossiking agent. Thus, it is seen that the various crossiking agents will be operatble in different degrees of ficiency depending on the olefins which are copolymered with maleic anhydride. Of course, all of the vinyl eters of the olefinically unsaturated carboxylic acids iving 3 to 24 carbon atoms will be operable as crossriking agents in varying degrees with the olefin-maleic ihydride copolymers. This is contrasted to divinyl benne and a number of other compounds which might be :pected to be good cross-linking agents but which are at operable at all as eross-lyinking agents with these lefin and maleic anhydride comonomers. Generally ieaking the molecular weight of the interpolymer formed 1d/or degree of cross-linking decreases with increasing :mperature and increases with increasing pressure. This borne out by the data of Table I. Also the larger the nount of cross-linking agent which is used the greater ill be the degree of cross-linking. It should be noted that The reaction timewas about 14% hours, and the yield of polymer was 383 grams.

A specific viscosity determination was attempted on the polymer produced in Example 10 but it was found that 1% of this polymer formed an insoluble gel in dimethylformamide, so no specific viscosity determination was possible.

A sample of the polymer of Example 10 was added to suflicient water containing sodium hydroxide to make up a 1 /2% concentration of the polymer in water, the sodium hydroxide having been added in sufficient amount to neutralize the maleic anhydride copolymer forming substantially the disodium salt of the polymer and giving a pH of 10.42. The resulting dispersion of the po1ymer salt in water was tested for viscosity with a Brookfield viscosimeter using a number 4 spindle and at 6 r.p.rn. The viscosity of the dispersion was 10,600 centipoises at room temperature (about 25 0.).

EXAMPLE 14 In a substantially identical manner to Example 2, the

1 the experiments summarized in Table I W re Carriefi'i- Maleic anhydride 196 grams. it in a similar manner to Examples 1, 2, 3, 4 n 5 Isobutylene 123 grams. hich are described in detail hereinabove. Wh re t Benzene 1600 cc. rookfield viscosity is greater than 100,0 0 61 th Salts Vinyl acrylate 3.0-8 grams. 1V6 been tested at the lower 1% and 0.5% cence Benzoyl peroxide 0.80 grams. ons as indicated in the table, in addition to the norm Temperature 80 C.

%% concentration. 1 Pressure Autogenous.

EXAMPLE 10 Theexperiment'of Example 10 was run ina substanally identical manner as that of Example fl, except that 1 Example 10, 3.43 grams of vinyl acrylate representig 1% by weight, 0.64 .mol percent, based on reacting I The amount of vinyl acrylate represents 1% by weight,

0.79 mol percent, based on reacting monomers, the re- As in Example 2, an attempted specific viscosity deter mination using 1% of the product polymer in dimethylformamide resulted in an insoluble gel, so no specific viscosity determination could be made.

In a similar manner to that described in Example 2, a l%% dispersion of the sodium salt of the polymer in water was prepared having a pH of 10.50. A frockfield viscosity determination of this aqueous dispersion gave a viscosity of 25,000 centipoises at room temperature (about (3.).

EXAMPLE 15 In a substantially identical manner to Example 2, the following experiment is carried out, except for changes in conditions and reactor charges indicated as follows:

Maleic anhydride grams 267 Ethylene p.s.i.g 4S0 Benzene cc 2089 Benzoyl peroxide grams 3.48 Vinyl linoleate do 9.36 Temperature C Reaction time hours 18 The amount of vinyl linoleate cross-linking agent is 0.56 mol percent (2.7 wt. percent) based on reacting mono mers. The polymer product obtained forms an insoluble gel at 1% concentration in dimethylform'amide, 3. 0 no specific viscosity can be made. The effectiveness of vinyl linoleate as a cross-linking agent is determined usixg the Brookfield viscosimeter method described in Exani ple 2.

EXAMPLE 16 This experiment is also carried out in a substantially identical manner to that of Example 2, except for changes in conditions and reactor charges indicated as follows:

Maleie anhydride grams 267 Ethylene p.s.i.g 450 Benzene cc 2089 Denzoyl peroxide grams 3.48 Divinyl itaconate do 5.57 Temperature C 60 Reaction time ..hours. 18

{Selection of optimum pH for thickening operations using alkali metal vs. amine bases for neutralization A. NEUTRALIZED 'ITH SODIUM HYDROXIDE TO SPECIFIED pH B. NEUTRALIZED WITH AMMONIUM HYDROXIDE TO SPECIFIED pH 'lhis crosslinked ethyleue-maleic anhydride interpolyrner was prepared as described in Example No. 2 with exception of reaction presure which was 275 p.s.i. and reaction temperature which was C.

Brookfield viscosity at room temperature for 1.5% aque ous solution No. a spindle.

T he data of Table II above show the viscositics dium hydroxide neutralized interpolymers and ammo hydroxide neutralized interpolymer at various This serves as a guide for neutralization to optimun cosities for these two different types of bases. In the of the alkali metal base, the preferred range is about about 11 pH, or possible 8 to about 10, but viscositie high at pH values as low as about 5. In the case 0 amine base viscosities are high'from pH 4 to abo Viscosities continue at a high level with addit amounts of added base, however, due to a bufferin tion the pH rise is small. The preferred pH rang these amine salts being about 5 to about 8.

The data in Table III below were obtained with t cne-maleic anhydride inter-polymers cross-linked will by weight based on reacting monomers of vinyl crot using 1% aqueous polymer salt solutions. The efl'e temperature and pressure of polymerization on the cosity of ammonium and sodium salt solutions of th terpolymers at or near optimum pH for maximum cosity is shown in this table. Viscosities were d mined in the usual manner using a Brookfield viscr eter.

Although the invention has been described in tern specific examples which are set forth in considerable tail. it should he understood that this is by way of i tration only and that the invention is not necessarily ited thereto since alternative improvements and open techniques will become apparent to those skilled in art in view of the disclosure. Accordingly, modifica'i are contemplated which can be made without depa' from the spirit of the described invention.

I claim:

1. A cross-linked interpolymer comprising substar ly equimolar portions of maleic anhydride and an 0 having from 2 to 4 carbon atoms, and a cross-lin agent which is a vinyl ester of an olefinically unsatur aliphatic carboxylic acid having from 3 to 24 ca: atoms in an amount in the range of about 0.1 mol cent to about 5 mol percent based on reacting monon 2. The interpolymer of claim 1, wherein the amoui said cross-linking agent is in the range of about 0. about 3 mol percent.

3. A cross-linked interpolymer comprising substar ly equimolar portions of maleic anhydride and an 0 having from 2 to 4 carbon atoms, and a cross-tin agent which is a vinyl ester of an olefinically unsatur aliphatic carboxylic acid having from 3 to 24 car atoms in at least an amount sufiicient to make said it polymer substantially insoluble in dirnethylformamid 25 C.

4. The interpolymer of claim 3, wherein said ci linking agent is vinyl acrylate.

S. The interpolymer of claim 3, wherein said olefi ethylene and said cross-linking agent is vinyl crotor 6. The interpolymer of claim 3, wherein said olefi ethylene and said cross-linking agent is vinyl linoleat 7. The interpolymer of claim 3, wherein said olcfi ethylene and said cross-linking agent is divinyl itacor 8. A composition of matter comprising an aqueous persion of from about 0.1% to abut 15% by weight salt selected from the class consisting of alkali metal line salts of a cross-linked interpolymer of substantially dium salt, said olefin is ethylene, and said cross-linking uimolar portions of maleic anhydride and an olefin havagent is vinyl crotonate. g from 2 to 4 carbon atoms, and a cross-linking agent 18. A salt selected from the class consisting of alkali llCh is a vinyl ester of an olefinically unsaturated a1i metal and amine salts of a cross-linked interpolymer of atic carboxylic acid having from 3 to 24 carbon atoms substantially equimolar portions of maleic anhydride and an amount in the range of about 0.1 mol percent to an olefin having from 2 to 4 carbon atoms, and a crossout 5 mol percent based on'reacting monomers. linking agent which is a vinyl ester of an olefinically un- 9. The composition of claim 8, wherein said salt is saturated aliphatic carboxylic acid having from 3 to 24 :sent in an amount of between about 0.25% to about carbon atoms in an amount in the range of about 0.1 by weight, said cross-linking agent is present in mol percent to about 5 mol percent based on reacting ount of between 0.3 mol percent and about 3 mol permonomers. it. 19. A salt of claim 18 wherein said cross-linking agent 10. The composition of claim 9, wherein the pH is in is present in an amount of between 0.3 mol percent and range of about 5 to about 11 and said salt is an alkali about 3 mol percent. :tal salt. 15 '20. A salt of claim 18 which is an alkali metal salt. 11. A composition of matter comprising an aqueous 21. A salt selected from the class consisting of alkali persion of about 0.1 to about 15% of a salt selected metal and amine salts of a cross-linked interpolymer of m the class consisting of alkali metal and amine salts Substantially equimolar portions of maleic anhydride and a cross-linked interpolymer of substantially cquimola; an olefin having from 2 to 4 carbon atoms, and a crossrtions of maleic anhydride and an olefin having from 20 linking agent which is a vinyl ester of an olefinically uno 4 carbon atoms, and a cross-linking agent which is a saturated aliphatic carboxylic acid having from 3 to 24 iyl ester of an olefinically unsaturated aliphatic car carbon atoms in at least an amount sufiicient to make said xylic acid having from 3 to 24 carbon atoms in at least interpolymer substantially insoluble in dimethylformamamount sufficient to make said interpolymer substanide at 25 C. lly insoluble in dimethylformamide at 25 C. b 25 22. A salt of claim 21 which is an ammonium salt. 12. The composition of-claim 11, wherein said salt is 23. A salt of claim 21 which is a sodium salt.

ammonium salt present in an amount of betweer. 24. A salt of claim 23 wherein said cross-linking agent out 0.25% and about 10%, and the pH is in the range is vinyl acrylate. about 4 to about 10. 25. A salt of claim 23 wherein said cross-linking agent 13. The composition of claim 11, wherein said salt is is vinyl crotonate and said olefin is ethylene. sodium salt present in an amount of between about 26. A salt of claim 22, wherein said cross-linking agent 15% and about 10%, and the pH is in the range of is vinyl crotonate and said olefin is ethylene. out 5 to about 11. 14. The composition of claim 13, wherein said cross- References Cited in the file of this P king agent is vinyl acrylate. UNITED STATES PATENTS I 15. The composition of claim 13, wherein said olefin 2,202,846 Garvey et June 4, 1940 ethylene and said cross-linking agent is vinyl crotonate.

16. A method of printing textile fabric which comprises 2378629 Hanford June 1945 ating said fabric with a printing paste comprising a 2449489 Larson Sept 1948, [oring material and an aqueous dispersion of about 40 2519348 Bums "5" 195 to about 15 of a salt selected from the class con- 2533635 Seymour 195C ting of alkali metal and amine salts of a cross-linked 2599371 Chadderton June 1952: erpolymer of substantially equimolar portions of male- 2? Seymour 1953 anhydride' and an olefin having from 2 to 4 carbon Brawn July 1956 )ms, and a cross-linking agent which is a vinyl ester of FOREIGN PATENTS olefinically unsaturated aliphatic carboxylic acid hav-- 496,650 I Canada Oct 6, 1953 g from 3 to 24 carbon atoms in at least an amount sufient to make said interpolymer substantially insoluble OTHER REFERENCES dimethylformamide at 25 C., and drying said fabric. The Borden Company, Monomer-Polymer Laborato- 17. The method of claim 16, wherein said salt is sories, Price List, Jan. 1, 1958, page 15, 

1. A CROSS-LINKED INTERPOLYMER COMPRISING SUBSTANTIALLY EQUIMOLAR PORTIONS OF MALEIC ANHYDRIDE AND AN OLEFIN HAVING FROM 2 TO 4 CARBON ATOMS, AND A CROSS-LINKING AGENT WHICH IS A VINYL ESTER OF AN OLEFINICALLY UNSATURATED ALIPHATIC CARBOXYLIC ACID HAVING FROM 3 TO 24 CARBON ATOMS IN AN AMOUNT IN THE RANGE OF ABOUT 0.1 MOL PERCENT TO ABOUT 5 MOL PERCENT BASED ON REACTING MONOMERS. 